1. Field of the Invention
The present invention relates to a multilayer nonwoven fabric including a plurality of layers.
2. Related Art
Nonwoven fabrics have been conventionally employed in a wide range of fields, for example, sanitary materials such as disposable diapers and sanitary napkins, cleaning supplies such as wipers, and medical supplies such as masks. The nonwoven fabrics have been thus employed in different fields. When the nonwoven fabrics are actually employed for products in various fields, however, they must be manufactured so as to have properties and structures suitable for respective applications of the products.
In recent years, demand for multilayer nonwoven fabrics designed so as to have desired functions by laminating a plurality of nonwoven fabrics has increased. It is required that the multilayer nonwoven fabrics are manufactured so as to have shapes and structures suitable for respective applications of the products.
On the other hand, Japanese Patent Publication No. 3587831, for example, proposes a multilayer nonwoven fabric, in which a plurality of raised ridge portions are formed on a first fiber layer, serving as a surface sheet used for a skin abutted surface of an absorbent article and manufactured by heating multilayer fibers obtained by laminating the first fiber layer and a second fiber layer including latent crimped fibers and partially thermally fusing the first fiber layer and the second fiber layer at a plurality of positions.
However, the multilayer nonwoven fabric is a multilayer nonwoven fabric manufactured by heating multilayer fibers obtained by laminating a first fiber layer and a second fiber layer containing latent crimped fibers and thermally fusing the first fiber layer and the second fiber layer at a plurality of positions. In the multilayer nonwoven fabric, the second fiber layer heat-shrinks so that slack occurs in the first fiber layer, to form a large number of raised ridge portions. The second fiber layer heat-shrinks in a horizontal direction (a plane direction) so that the size thereof is reduced while maintaining a sheet shape, while the above-mentioned slack in the first fiber layer constitutes the raised ridge portions. Here, the raised ridge portions are formed of only the first fiber layer. When the first fiber layer is composed of flexible fibers in the multilayer nonwoven fabric, however, the raised ridge portions may be easily crushed by the application of pressure or the like. That is, this multilayer nonwoven fabric is superior in original feeling. However, the raised ridge portions are easily crushed during use so that the ratio of contact with the skin may, in some cases, be increased. As a result, a user may experience a foreign-body sensation or excreta may more readily adhere to the user's skin.